Method for producing a laser marking on reflective material

ABSTRACT

A method for producing a laser mark on reflective material by a laser beam is provided, wherein a plurality of images on the same laser mark can be observed only from different view angles. The method includes the steps of selectively vaporizing the sides of each group of reflective bodies to form rough surfaces by a laser beam with a certain incident angle, and then selectively vaporizing another side of said each group of reflective bodies to form rough surfaces by a laser beam with another incident angle. Due to the different reflectivity of the rough surfaces and the unrough surfaces, dark spots and bright spots are respectively formed and hence constitute pictures. Therefore, different images may be recorded and shown on the same reflective body by means of more than one surfaces thereof. The commercial reflective material can be used in the method of the invention, so that middle or small manufacturers can produce laser marks with high quality, low cost, excellent optical effect and high difficulty of counterfeit by common computers and laser scanning devices.

FIELD OF THE INVENTION

The present invention relates to a method for producing a visible markon reflective material by laser beams, more particularly to a method forproducing a laser mark on reflective material of a base object by laserbeams, wherein a plurality of images on the same laser mark can beobserved only from different view angles.

BACKGROUND OF THE RELATED ART

The marks (markings, also referred as “labels”) used for products shallbe beautiful and durable, and more important to prevent themselves fromcounterfeit. Therefore, laser marks used for some brand-name productsare usually produced greatly difficultly. Some laser marks with patternsand characters are produced on the ready-made commercial reflectivematerial by laser beams. For the laser marks on clothes, the reflectivematerial such as cloth base, plastic film base and the like is generallyused so that these laser marks can be washed together with the clothesmany times.

As shown in FIG. 1, the generally commercial reflective material 100 iscomposed of a base body 11, reflective bodies 12 and a support layer 13by which the reflective bodies are fixed on the base body. The base body11 may be clothes, paper or plastic film and the like, while thereflective bodies 12 may be spherical transparent objects. In the casethat the reflective bodies are spherical, the reflex action (reflectedlight) is obtained by the support layer indeed since the reflectivebodies can only refract light. In the structure shown in FIG. 1, theincident light rays from any direction will be reflected back in thesame direction.

The reflex action of a polyhedral reflective body 14 is different fromthat of the spherical reflective body 12. As shown in FIG. 2, thepolyhedral reflective body 14 may be a tetrahedral reflective body.Specifically, the incident light rays normal to one surface (i.e.incident surface) of the tetrahedral reflective body are total reflectedback by the inner side of the tetrahedral reflective body, and then aredirected out from the incident surface. So, the reflection principlesshown in FIG. 1 and FIG. 2 are absolutely different.

The methods for producing a visible mark on reflective material by laserbeams have been known for a long time. For example, U.S. Pat. No.6,231,196 B1 filed in 1997 discloses a method for simply vaporizing partof the light reflective substance on the associated region of thereflective material by laser beams so as to form a mark with darkpatterns and characters on a bright background. U.S. Pat. No. 6,217,175B1 filed in 1998 discloses an improved method for flattening the bottomsof the spherical reflective bodies on the associated region of thereflective material by laser ablation, so that the observer can see thedark patterns and characters in a direction normal to the plane of thereflective material, while the observer cannot see any pattern orcharacter but only a bright background from a direction deviating fromthe normal direction with a certain angle.

FIG. 3 is a view for illustrating the reflection principle of sphericalreflective bodies 12 in the prior art, each having a flat bottom formedby laser ablation. As shown in FIG. 3, the bottoms of the sphericalreflective bodies 12 are made to be plane, and there is not a supportlayer to play a reflective role. Thereby, when incident light rays enterthe reflective material in a direction normal to the reflectivematerial, they will not undergo the reflection, thus, no reflectivelight rays but dark patterns and characters can be seen by the observerwithin a certain range, such as 30° shown herein, which depends on thediameter of the plane. And no patterns and characters but a brightbackground can be seen if out of this range. Thus, the method in theprior art is just to destroy the reflective characteristic of thebottoms of the associated spherical reflective bodies 12, that is, todestroy the reflective characteristics of the first emergent surface andthe second incident surface for the incident light rays, so that theincident light rays cannot be reflected back thereon. Since eachspherical reflective body 12 has only one bottom, the method in theprior art can only produce at most one mark on the same sphericalreflective body 12.

The mark produced by the first method is so easy to be faked. Inaddition, while the reflective substance is vaporized by the laser beamnormal to the reflective material, the bared support layer around thereflective substance tends to be damaged by the laser beam. Actually,this method doesn't bring any special optical effect, just like etchinga mark on a surface of a bowl. The above-mentioned second method can notbe applied to polyhedral reflective bodies but only to the sphericalreflective bodies, although it can bring a certain optical effect.Furthermore, it is inconvenient to flatten the bottom of ready-made thespherical reflective bodies of opaque base-body reflective material. Andthis process may destroy the original base body of the reflectivematerial. Therefore, it is unpractical for the middle and smallmanufacturers to accept this method since they often purchase theready-made reflective material. To get things worse, the structuralcharacteristic of the reflective material cannot be fully utilized, sothe laser mark is not difficult to counterfeit.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a simple method forproducing a laser mark on the ready-made reflective material, which canovercome the disadvantages that the method in the prior art iscomplicated and thereby is too difficult to use ready-made reflectivematerial; its process is only applicable to spherical reflective bodies;and its optical effect is not good and it is easy to counterfeit. By themethod according to the invention, laser marks made of the ready-madereflective material which is purchased by the manufacturers can bedesigned and produced with excellent optical effect and high difficultyof counterfeit.

The above-mentioned object of the invention may be achieved by thefollowing measures:

A method for producing a laser mark on reflective material, by which thelaser mark provided with a pattern that may be processed and observed isformed on the reflective material with reflective bodies, characterizedin that in accordance with the pattern an laser beam selectively scansand irradiates the reflective bodies at an incident angle, so that theirradiated surfaces of the reflective bodies are vaporized to form roughsurfaces, while the nonirradiated surfaces of the reflective bodies arestill of reflective surfaces, thereby the pattern is formed on the lasermark through the combination of the dark spots corresponding to therough surfaces and the bright spots corresponding to the reflectivesurfaces, and may be observed at the incident angle of the laser beam.

In the method, a laser beam selectively scans and irradiates the sidesof a selected group of reflective bodies at an incident angle, so thatthe irradiated surfaces of the reflective bodies are vaporized to formfirst rough surfaces, and then a laser beam selectively scans andirradiates the sides of another selected group of reflective bodies atanother incident angle, so that the irradiated surfaces of thereflective bodies are vaporized to form second rough surfaces, whereinthe first rough surfaces and the second rough surfaces overlapincompletely, and the nonirradiated surfaces of the reflective bodiesare still of reflective surfaces, thereby two patterns are formedrespectively on the laser mark through the respective combination of thedark spots corresponding to the first rough surfaces or the dark spotscorresponding to the second rough surfaces and the bright spotscorresponding to the reflective surfaces, and may be observedrespectively at the incident angles of the two laser beams.

The incident angle is selected in a range from 10° to 80°.

The two incident angles are the same.

The two incident angles are different.

The method further includes the step that a laser beam selectively scansand irradiates the sides of a n^(th) selected group of reflective bodiesat a n^(th) incident angle, so that the irradiated surfaces of thereflective bodies are vaporized to form a n^(th) rough surfaces, whereinthe first to n^(th) rough surfaces overlap incompletely with each other,and the nonirradiated surfaces of the reflective bodies are still ofreflective surfaces, thereby n patterns are formed respectively on thelaser mark through the respective combination of the first dark spotscorresponding to the first rough surfaces, the second dark spotscorresponding to the second rough surfaces till the n^(th) dark spotscorresponding to the n^(th) rough surfaces and the bright spotscorresponding to the reflective surfaces, and may be observedrespectively at the incident angles of the n laser beams, wherein n isan integer more than 2.

The n incident angles are the same.

The n incident angles are different.

The reflective bodies are spherical.

The reflective bodies are polyhedral.

The invention has the advantages over the prior art as follows:

1. By using the method for producing a laser mark on the reflectivematerial according to the present invention, a plurality of patterns maybe formed on the same reflective material by means of the structuralcharacteristic of the reflective material, thereby the different imageson the laser mark may be observed from different angles.

2. The ready-made commercial reflective material having sphericalreflective bodies or polyhedral reflective bodies can be used in themethod according to the invention.

3. The laser mark with excellent optical effect and high difficulty ofcounterfeit can be produced by the method according to the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of conventional reflective material withspherical reflective bodies;

FIG. 2 is a view for illustrating the reflection principle inconventional reflective material with polyhedral reflective bodies;

FIG. 3 is a view for illustrating the reflection principle in sphericalreflective bodies in the prior art, each having a flat bottom formed bylaser ablation;

FIG. 4 is a schematic view for illustrating a state that a mark isformed on a reflective material by laser ablation according to themethod of the invention;

FIG. 5 is a schematic view for illustrating different incident angles oflaser beams selected in the method of the invention; and

FIG. 6 is a view for illustrating optimum modes for observing the lasermark produced by the method of the invention.

DESCRIPTION OF PREFERRRED EMBODIMENTS

FIG. 4 is a schematic view for illustrating a state that a mark isformed on reflective material by laser ablation according to the methodof the invention. Although there are spherical reflective bodies 12shown in FIG. 4, the method is also applicable for polyhedral reflectivebodies 14. The laser beams can irradiate at least a range larger thanthe spherical surface of one reflective body 12. In the invention, thelaser beams shown in FIG. 4 do not irradiate the reflective bodies 12 ina direction normal to the bottoms of the reflective bodies 12, butirradiates first incident surfaces of the upper portions of thereflective bodies 12 at any oblique incident angle, for example between10° to 80°. Accordingly, the minor rough areas caused by vaporizationare formed on the first incident surfaces so that the incident lightrays are scattered or refracted in several directions, instead ofreflected toward the incident direction. Hence, while the mark isobserved in the incident direction, the rough areas caused byvaporization are shown as dark spots and the other areas nonirradiatedby the laser beams are shown as bright spots. The advantage of the laserbeams obliquely irradiating the reflective bodies is that there are atleast two irradiated surfaces BD and AC overlapping incompletely witheach other on the same spherical reflective body 12, wherein thecambered surface CD is an overlapping portion and the cambered surfacesBC and AD are nonoverlapping portions. Thus, two different marks may beformed in the following way. Firstly, the certain sides of each group ofreflective bodies are selectively vaporized by a laser beam with anincident angle to form rough surfaces, and then another certain sides ofsaid each group of reflective bodies are selectively vaporized by alaser beam with another incident angle to form rough surfaces. Since therough surfaces and unrough surfaces are shown as dark spots and brightspots respectively due to the different reflectivity therebetween, a lotof dark spots and bright spots with different distribution densities canconstitute a picture. Therefore, different images can be recorded andshowed by means of more than one surfaces on the same reflective body.

In addition, according to the pattern of the laser mark, another groupof reflective bodies may be selected, and then the surfaces of theselected group of reflective bodies are irradiated by a laser beam withan incident angle. Accordingly, another combination of rough surfacesand unrough surfaces is created so that a pattern of another image isformed.

Hence, a laser mark with a plurality of images, which can be observedonly from different view angles, may be formed on the reflectivematerial by laser beams.

Similarly, as long as the reflective bodies still have unrough surfaces,a plurality of different patterns may be formed theoretically, but thedistinguishability will be lower.

If the reflective bodies are polyhedral bodies, a larger number ofpatterns may be formed on the same reflective material due to thedifferent postures of polyhedral bodies, but their luminosity andcontrast will become poorer.

FIG. 5 is a schematic view for illustrating different incident angles oflaser beams selected in the method of the invention. In FIG. 5, fivespherical reflective bodies 12-1, 12-2, 12-3, 12-4 and 12-5 are shownfrom right to left. The upper half arc of the spherical reflective body12-2 is irradiated by the laser beams with an incident angle of 30° fromleft and right sides. As shown in FIG. 5, for the right upper halfportion of the spherical reflective body, only the cambered surfacebetween the intersection point A, which is formed by the surface of thespherical reflective body 12-2 and the lowermost light ray from theright side, and the tangent point D, which is formed by the surface ofthe spherical reflective body 12-2 and the uppermost light ray from theleft side, is not irradiated by the two laser beams together. That is,the cambered surface is irradiated only by the laser beam from the rightside. Similarly, the spherical reflective body 12-3 is irradiated by thelaser beams with an incident angle of 45° from left and right sides, andthe spherical reflective body 12-4 is irradiated by the laser beams withan incident angle of 60° from left and right sides. Thereby, the largerthe incident angle is, the larger the nonoverlapping area (i.e. ADcambered surface) of left-side and right-side light rays is, and thelarger the nonirradiated area is. The spherical reflective body 12-5 isirradiated by the laser beams with an incident angle of 30° from rightside and an incident angle of 60° from left side. Although there is thelargest nonoverlapping area AD at the right upper half of the sphericalreflective body 12-5, no nonoverlapping area exists on the left upperhalf thereof. Therefore, it is preferable that each of the incidentangles of the left-side and right-side laser beams is 45° and therebyboth the left and right marks can have the optimum resolution.Certainly, for the sake of secrecy, the difficulty of counterfeit willbe increased because of using the left-side and right-side laser beamswith different incident angles.

Although the overlapping area of the left-side and right-side light raysis large on the top of each spherical reflective body in FIG. 5, a largeamount of light rays will be reflected out and only a little light rayscan enter the spherical reflective body when the light rays irradiatethe medium such as glass and the like with a large incident angle. Thus,the phenomenon that the left-side and right-side light rays overlap eachother is not so serious as that shown in FIG. 5.

The computer and the laser generator employed in the method of thisinvention are well known. For example, the laser generator may be NdYAG,CO₂ or diode-pumped laser generator and the like, and the computer isused to control the laser generator and the laser reflection scanningdevice. The reflective material tape on the market is often in a roll.When the reflective material tape is transferred by an intermittent typereel device and stopped at the processing position, the tape is scannedand processed by laser beams. When the laser beams with appropriateintensity scan each group of reflective bodies 12 or 14 in turn, theirradiated surfaces of the group of reflective bodies become rough byvaporization. Thereby, the group of reflective bodies will be observedas dark spots from this angle, and the unscanned reflective bodies willbe observed as bright spots. A lot of dark spots and bright spots withdifferent densities constitute a picture. In order to increase theproduction speed, it is preferable that one laser device is used as theleft-side light source and the other laser device is used as theright-side light source. If the area of a laser mark is of 1.5 cm heightand 5.0 cm width and the energy of the laser beams is 10 watt, thescanning process can be completed in 30 seconds. These are justexperimental data of the invention. In fact, the processing time may bedifferent due to the quality of the reflective material, the complexityof the pattern, the type of the laser, the angle of the incident lightrays and the like.

While being examined or watched, the laser mark 100 produced by themethod according to the invention can be most clearly observed only oncondition that the illuminating light rays irradiate the mark 100 in thedirections of the laser beams for processing and the observer looks themark 100 from the said directions too, as shown in FIG. 6. For example,as shown in FIG. 6, the image of the right portion of the laser markaccording to the invention is formed by the laser beam scanning with anincident angle of 60°, and thus the optimum observation effect can beobtained only on condition that both the illuminating light rays(indicated by a electric torch in FIG. 6) and the observer (indicated byan eye) are in the direction of the laser beam with an incident angle of60°. The image of the left portion of the laser mark shown in FIG. 6 isformed by the laser beam scanning with an incident angle of 30°, andthus the optimum observation effect can be obtained only on conditionthat both the illuminating light rays and the observer are in thedirection of the laser beam with an incident angle of 30° In FIG. 6, theimages in the bright background observed from two different directionsare completely different, for example one is a character and the otheris a pattern.

Herein, the “incident angle” in the description refers to an acute anglebetween the direction of the incident light rays and the directionnormal to the plane of the reflective material.

INDUSTRIAL APPLICABILITY

By using the method for producing a laser mark on reflective materialaccording to the present invention, a mark with a plurality of patternsmay be formed on the same reflective material by means of the structuralcharacteristic of the reflective material, so that different images onthe laser mark may be observed from different view angles. Theready-made commercial reflective material having spherical reflectivebodies or polyhedral reflective bodies can be used in the method of theinvention. The laser mark with excellent optical effect and highdifficulty of counterfeit can be produced by the method according to thepresent invention.

1. A method for producing a laser mark on reflective material, by whichthe laser mark provided with a pattern that may be processed andobserved is formed on the reflective material with reflective bodies,characterized in that in accordance with the pattern an laser beamselectively scans and irradiates the reflective bodies at an incidentangle, so that the irradiated surfaces of the reflective bodies arevaporized to form rough surfaces, while the nonirradiated surfaces ofthe reflective bodies are still of reflective surfaces, thereby thepattern is formed on the laser mark through the combination of the darkspots corresponding to the rough surfaces and the bright spotscorresponding to the reflective surfaces, and may be observed at theincident angle of the laser beam.
 2. A method according to claim 1,characterized in that a laser beam selectively scans and irradiates thesides of a selected group of reflective bodies at an incident angle, sothat the irradiated surfaces of the reflective bodies are vaporized toform first rough surfaces, and then a laser beam selectively scans andirradiates the sides of another selected group of reflective bodies atanother incident angle, so that the irradiated surfaces of thereflective bodies are vaporized to form second rough surfaces, whereinthe first rough surfaces and the second rough surfaces overlapincompletely, and the nonirradiated surfaces of the reflective bodiesare still of reflective surfaces, thereby two patterns are formedrespectively on the laser mark through the respective combination of thedark spots corresponding to the first rough surfaces or the dark spotscorresponding to the second rough surfaces and the bright spotscorresponding to the reflective surfaces, and may be observedrespectively at the incident angles of the two laser beams.
 3. A methodaccording to claim 1, characterized in that the incident angle isselected in a range from 10° to 80°.
 4. A method according to claim 2,characterized in that the two incident angles are the same.
 5. A methodaccording to claim 2, characterized in that the two incident angles aredifferent.
 6. A method according to claim 2, characterized in that alaser beam selectively scans and irradiates the sides of a n^(th)selected group of reflective bodies at a n^(th) incident angle, so thatthe irradiated surfaces of the reflective bodies are vaporized to form an^(th) rough surfaces, wherein the first to n^(th) rough surfacesoverlap incompletely with each other, and the nonirradiated surfaces ofthe reflective bodies are still of reflective surfaces, thereby npatterns are formed respectively on the laser mark through therespective combination of the first dark spots corresponding to thefirst rough surfaces, the second dark spots corresponding to the secondrough surfaces till the n^(th) dark spots corresponding to the n^(th)rough surfaces and the bright spots corresponding to the reflectivesurfaces, and may be observed respectively at the incident angles of then laser beams, wherein n is an integer more than
 2. 7. A methodaccording to claim 6, characterized in that the n incident angles arethe same.
 8. A method according to claim 6, characterized in that the nincident angles are different.
 9. A method according to claim 1,characterized in that the reflective bodes are spherical.
 10. A methodaccording to claim 1, characterized in that the reflective bodies arepolyhedral.